1. Field of the Invention
The present invention relates to a navigation system for a remote controlled actuator of a kind, which is used in medical and mechanical processing applications and capable of altering the attitude of a machine tool by remote control.
2. Description of Related Art
Remote controlled actuators are currently available; some are used in the medical field for osteo treatment and some are used in the mechanical processing field for drilling and cutting a bone. Any of those remote controlled actuators controls by remote control a machine tool fitted to a distal end of an elongated pipe of a linear or curved configuration. However, since the conventional remote controlled actuator is designed solely to control only the rotation of the machine tool by remote control, difficulties have been encountered in processing of a complicated shape and processing at a site difficult to view with eyes from the outside in the medical field. Also, in the drilling process, the capability of processing not only the linear line, but also the curved configuration is often required. In addition, in the cutting process, the capability is required to perform the process at a site deep in grooves. In the following description, conventional art and problems inherent in the remote controlled actuator will be discussed with reference to the medical field.
In the orthopedic field, the artificial joint replacement is well known, in which a joint, of which bone has been abraded by due to bone deterioration, is replaced with an artificial joint. The joint replacement surgery requires a living bone of a patient to be processed to enable an artificial joint to be implanted. In order to enhance the strength of postoperative adhesion between the living bone and the artificial joint, such processing is required to be performed precisely and accurately in conformity to the shape of the artificial joint.
By way of example, during the hip join replacement surgery, a thigh bone is opened to secure access of an artificial joint into the femoral marrow cavity. In order to secure a strength of contact between the artificial joint and the bone, surfaces of contact of the artificial joint and the bore must be large and so the opening for insertion of the artificial joint is processed to represent an elongated shape extending deep into the bone. As a medical actuator used in cutting the bone in a manner described above, the actuator is known, in which a tool is rotatably provided in a distal end of an elongated pipe and, on the other hand, a drive source such as, for example, a motor is mounted on a proximal end of the pipe so that the tool can be driven through a drive transmitting means disposed inside the elongated pipe. (See, for example, the Patent Document 1 listed below.) Since in this type of medical actuator a rotatable element that is exposed bare to the outside is only the tool at the distal end of the elongated pipe, the tool can be inserted deep into the bone.
The surgical operation for artificial joint replacement generally accompanies skin incision and muscular scission. In other words, the human body must be invaded. In order to minimize the postoperative trace, it is quite often desirable that the elongated pipe referred to above is not necessarily straight, but is moderately curved. To meet with this desire, the following technique has hitherto been suggested. For example, the Patent Document 2 listed below discloses the elongated pipe having its intermediate portion curved double to displace an axial position of the distal end of the pipe relative to the longitudinal axis of the proximal end of the same pipe. To make the axial position of the distal end of the pipe relative to the longitudinal axis of the proximal end of the same pipe is also known from other publications. Also, the Patent Document 3 listed below discloses the elongated pipe rotated 180°.
If in a condition, in which the artificial joint is inserted into an artificial joint insertion hole formed in the living bone, a large gap exist between the living bone and the artificial joint, a large length of time is required to accomplish the postoperative adhesion between the living bone and the artificial joint and, therefore, it is considered desirable that the gap should be as small as possible. Also, it is important that respective surfaces of contact between the living bone and the artificial joint be smooth, and accordingly, a high precision is required in processing the artificial joint insertion hole. Whatever the pipe take any shape, the working range of the tool is limited by the shape of the pipe and, therefore, it is difficult to widen the working range of the tool to process the artificial joint insertion hole so that the living bone and the artificial joint may can have smooth contact surfaces and, yet, the gap between the living bone and the artificial joint may be small while skin incision and muscular scission are minimized at the same time.
In general, it is quite often that the patient's bone, where an artificial joint is to be implanted, exhibits a strength lowered as a result of aging and, in a certain case, the bone itself is deformed. Accordingly, the processing of the artificial joint insertion hole is more difficult to achieve than generally considered.
Where the artificial joint insertion hole is to be processed in the bone with the use of the remote controlled actuator, it is quite often that the tool cannot be directly viewed with eyes and, therefore, a tool tip position detecting device is needed in order to detect the tip position of the tool. As a method to measure a position of a bone which is an object to be processed, the following techniques have hitherto been well known in the art.
The Patent Document 4 listed below discloses the navigation system, in which a marker is applied to the bone so that the position of the bone can be measured by the detection of the marker with the use of an optical sensor. Using this technique, when a marker is applied not only to the bone, but also to the body of a remote controlled actuator, which is a stationary portion of such actuator, respective positions of the bone and the actuator main body can be measured.
The Patent Document 5 also listed below discloses the navigation system, in which a marker, which is formed in a specific pattern, not in a dot, is applied to the remote-controlled actuator main body so that both of the position of the marker and the attitude of the remote-controlled actuator main body to which the marker has been applied can be detected by the detection of the pattern of that marker with the use of a marker detecting unit. Once the attitude of the remote-controlled actuator main body is determined, the tip position of the tool can be estimated from the relative positional relation between the tip position of the tool and the site of the remote-controlled actuator main body where the marker has been applied. It is, however, to be noted that the relative positional relation between the tip position of the tool and the site of the remote-controlled actuator main body where the marker has been applied is measured beforehand and is recorded and stored as a positional relational information.
It occurs quite often that the tool is replaced with a different type thereof depending on an object to be processed and/or upon, for example, wear, and, therefore, the positional relational information to be used in estimation of the tip position of the tool is needed to be updated each time the replacement takes place. As such the Patent Document 5 discloses the use of a switch operatively linked with removal of the tool to provide a piece of information with which the operator of the remote controlled actuator can be informed of the necessity of updating of the positional relational information.
The Patent Document 6 listed below discloses the navigation system, in which a second marker different from a first marker fitted to the remote controlled actuator main body is prepared for use and in which the tip end of the tool is brought into contact with the second marker and, using a positional relation between the remote-controlled actuator main body and the second marker then measured, the tip position of the tool is estimated on the basis of the positional relation between the remote-controlled actuator main body and the first marker measured during the procedure.